This invention generally relates to control of a paper-feeder of a facsimile (FAX) system, and more particularly, to a control method for precise feeding of the document to the scanning point of the FAX system.
In order to transmit the contents of a document or to perform a self-copying function, using the FAX, the document, in general, must be fed via a document guide.
Once the document has been fed to the document guide, the FAX system drives an internal document feeding step motor (T.sub.X M) to locate the front-end of the document at a given position, and then scans the document for transmission or copying.
FIG. 1 shows a system block diagram of a known FAX system, in which a numeral reference 12 is a main control unit (MCU) which includes a timer having the functions of RTC (Real Time Clock), DMA (Direct Memory Access) for direct accessing of the memory, and a CPU (Central Processing Unit) for controlling the system, and which supervises the system to control input/output (I/O) related to the operation of the FAX. The numeral reference 14 represents a memory unit, which provides a program data under the control of the MCU 12, and stores the I/O data thereinto. The numeral reference 16 represents a sensor which detects the feeding of the document or the end of document (EOD), in order to generate a detection signal. The numeral reference 18 is a motor driver which drives a transmission motor T.sub.X M, or a receiving motor R.sub.X M, under the control of the MCU 12. Being supplied with a predetermined power, the numeral reference 20 is an FL (fluorescent) driver for driving a fluorescent (FL) lamp, under the control of the MCU 12. The numeral reference 30 represents an optic lens and a CCD (Charge Coupled Device) 32 performs photo-electrical conversion of the light signal passed through the lens 30 into an electrical signal, for output as serial data.
An image-signal processor 34 then includes an AGC (Automatic Gain Control) circuit and ACC (Automatic Contrast Control) circuit. It is an image processing unit which samples and holds the output data of the CCD 32, controls automatic gain and contrast to perform the analog-to-digital (A/D) conversion, supplying the MCU 12 with the Digitalized data. A plurality of I/O interfaces 24, 26 and 28 interface the MCU 12 with the sensor 16, the MCU 12 with the motor driver 18, and the MCU 12 with the FL driver 20, respectively. The fluorescent (FL) lamp, connected to the FL driver 20, operates under the control of the FL driver. In addition DOC represents a document, and the numeral reference 29 is a mirror.
Referring to FIG. 2, it shows a flow-diagram of a known method for controlling the paper feeding driver. The traditional controls for the paper-feeding driver are described hereinbelow by referring to FIGS. 1 and 2.
As will be apparent from the drawings accompanied, if the FAX as shown in FIG. 1 is supplied with power, it goes into the standby mode by the control of the MCU 12. The word `standby mode`, which is recommended by CCITT (Comite Consultatif International Telegraphique et Telephonique), represents the condition in which the FAX is able to either transmit or receive a document. If it goes into the standby mode, it reads the I/O interface IOF for a designated period of time, to test for detection of document feeding. In the case that no document is fed, it remains in the standby mode. If, whilst in the standby mode, a document is fed and a document-feed signal is generated from the sensor 16, the signal is transferred to MCU 12 through IOF.sub.1 24, and the MCU 12 applies a FL ON/OFF control data into IOF.sub.3 28.
The FL driver 20 is operated by the FL ON/OFF control data, and preheats to turn on the fluorescent lamp 22 on. The exposure of light on the front frame (FRFRM) is initiated by the turning-on of the fluorescent lamp and enters into the CCD 32 via the mirror 29 and lens system 30. The CCD 32 performs photo-electrical conversion to supply the converted signal to the image signal processor 34. The image signal processor 34 performs the digital signal processing in accordance with the commands of the MCU 12, and enters the result into the MCU 12.
The MCU 12 stores the input image data in the memory 14. The intensity of the scanning light on the front frame (FRFRM) becomes the reference waveform. The MCU 12, which has stored the reference intensity of the front frame (FRFRM) through the above operation, outputs the transmission motor driving data to IOF.sub.2 26 for a specified period and moves the inserted document in the subscanning direction.
The motor driver 18, which is driven by the transmission motor driving the data input through IOF 26, drives the transmission motor T.sub.X M to move the document in the subscanning direction. The MCU 12, which has driven the transmission motor T.sub.X M for a specified duration, stops the motor and shifts into the standby mode to detect the entry from the COPY/SEND keys via a data-bus (KDB). It remains in the standby mode while continuously monitoring the entry from COPY/SEND keys. In the above procedure, said specified duration for driving the motor means the period in which the document (DOC) can reach the scanning point from the position of the document feed detection sensor 16.
If the COPY/SEND key is pressed during detection of the entry from the key, the MCU 12 outputs the transmission motor drive data to the IOF.sub.2 26 to drive the transmission motor T.sub.X M and starts the scanning; that is to read the image signal of the document using the CCD 32 and image signal processor unit 34.
The traditional operating method, as described above, drives the transmission motor T.sub.X M in a step-by-step fashion after detection of document feed, and moves the document by rotating a driver roller (not shown), which rotates in accordance with the rotation of the transmission motor T.sub.X M. Therefore, the following problems can result:
The driver roller that is used to move the document is made of rubber and is sensitive to any changes in humidity, temperature, and the quality of paper (i.e., the quality of document). Therefore, changes in frictional force causes a drift in the starting point for scanning. In addition, it is not easy to design an optical mechanism allowing a short distance between the driver roller and the front frame, while accurately adjusting the starting point for scanning.